Recent studies have implicated environmental polymorphism as an important parameter in the interpretation of existing genetic polymorphism, especially allozymic polymorphism. We are attacking the question from two angles: (1) theoretical modeling of evolution dynamics in the presence of environmental variation and (2) experimental investigations of the relative sensitivity of various genotypes to environmental hazards. In cooperation with statisticians in the Environmental Biometry Branch and geneticists at North Carolina State University, we are analyzing gene frequency changes in response to insults of environmental chemicals. This will give some indication of the responsiveness of gene frequencies to environmental contamination.